Traditional gear systems are used to reduce or increase rotational shaft speed, along with resulting effect on shaft torque. A typical application for such a gear system is to a weak electrical motor in order to increase shaft torque. However, with a traditional gear system, there are often mechanical limitations due to, e.g., friction, wear, and temperature sensibility. Temperature changes can degrade gear mesh geometry and lubrication properties. These problems could be minimized, if not eliminated entirely, by using non-contacting, magnet elements in the gear system. Another benefit could be reduced mechanical and torque noise.
Biaxial gear systems have been previously patented, such as in U.S. Pat. Nos. 3,523,204 (to Rand Aug. 4, 1970) and 6,047,456 (to Yao et al. Apr. 11, 2000). The biaxial gear systems in these patents are inefficient and also likely have torque cogging problems when torque transmission loads are low.
In other applications, internal gear topology causes a higher number of magnet interactions between the drive and driven gears, which aids torque capability. Frank Jorgensen, in his article “The Cycloid Permanent Magnetic Gear,” IEEE Transaction on Industry Applications, November 2008, shows effectiveness of such magnetic gearing with cycloidal arrangement. The magnets are arranged such that at the region of closest approach, non-contacting, strong magnetic attractive forces are developed. As a result, there is a strong rotation transmission torque along with high torsional stiffness. The article details the analysis used to estimate the torque transmission characteristics; however, it does not address the high radial forces which must be reacted by the support bearing sets. It is apparent to those skilled in the art that the high bearing loads, which are constant at all speeds, can have serious effects on torque efficiency. In addition, highly loaded bearings are subject to wear-out.